^(123)I-BMIPP在犬顿抑心肌中的摄取、清除和代谢

Kinetics and metabolism of ^(123)I-BMIPP in canine stunned myocardium

目的 利用12 3 I 15对碘苯基 3(R ,S)甲基十五烷酸 (BMIPP)在犬顿抑心肌 (SM)中的不匹配分布 ,探讨其作为诊断SM示踪剂的可能性。方法 建立标准犬左回旋支 (LCX)顿抑心肌模型(18min结扎后再灌注 ,n =12 )。监测血流动力学和心功能参数。Doppler探头测量LCX血流和局部室壁收缩厚度 (WT)。SPECT显像和组织γ计数法测量局部心肌的BMIPP、2 0 1Tl分布和微球灌注(RBF)。测量局部心肌耗氧量、葡萄糖和乳糖利用率。动态测量局部BMIPP摄取与清除。薄层层析法分析BMIPP及其代谢产物。结果 心肌顿抑时的血流动力学参数和冠状动脉血流恢复到基础水平 ,但WT明显低于基础值 [(12 .9± 2 9.1) %和 (6 6 .3± 2 2 .4) % ,P <0 .0 1]。离体心脏SPECT显像示 ,顿抑心肌残留BMIPP[(70± 6 ) % ]高于2 0 1Tl[(6 6± 6 ) % ,P <0 .0 5 ]。SM组织计数则BMIPP[(88 5±6 0 ) % ]和Tl[(85 .4± 6 .7) % ]高于RBF[(70 .4± 10 .5 ) % ,P <0 .0 0 1]。SM中 ,2 0 1Tl与RBF相关性较好(r=0 .6 7) ,而BMIPP与RBF不相关 (r=0 .11)。虽然SM的局部耗氧量和乳糖利用率低于基础值 ,但BMIPP代谢产物清除增加。未经代谢的BMIPP摄取和清除均有减低趋势。结论 代谢因素对SM的BMIPP残留有明显影响 。

Objective Myocardial stunning has been proved to be associated with many clinical situations. No ideal approach was available for noninvasive diagnosis of myocardial stunning. The mismatched uptake of 123 I (15 (p iodophenyl) 3( R,S ) methylpentadecanoic acid (BMIPP) and thallium was clinically demonstrated in stunned myocardium. Discrepant results from animal model, however, raise a question of the reliability in the use of BMIPP for diagnosis of myocardial stunning. Methods A classic canine model of myocardial stunning was established. Regional uptake and retention of BMIPP and Tl were evaluated by SPECT imaging and tissue counting and were compared with regional myocardial blood flow (RBF) and wall thickening (WT). Regional metabolic parameters (including oxygen consumption, glucose and lactate utilization) were measured. Thin larger chromatography (TLC) was used for the analysis of BMIPP and its metabolites. The kinetics of the extraction of BMIPP and its products from both stunned and nonstunned territories were compared. Results A mismatched retention with higher BMIPP counts [(70±6)%] than Tl [(66±6)%, P <0.05] was found in stunned area on excised heart images. Though retention of BMIPP [(88.5±6.0)%] and Tl [(85.4±6.7)%] was matched well in stunned transmulral myocardium, both BMIPP and Tl activity was greater than RBF [(70.4±10.5)%, P <0 001]. In stunned myocardium, Tl showed a good correlation with RBF ( r =0.67), but BMIPP did not ( r =0 11). Despite of insufficient oxidation and utilization of lactate, the release of BMIPP products and washout of tissue radioactivity from stunned myocardium increased significantly. No evidence of increased BMIPP back diffusion was offered, since the proportion of intact BMIPP activity was always lower (though not significant) in the plasma from stunned territory. Conclusion These results suggest that metabolic factors (especially washout of products) have a significant effect on retention of BMIPP in stunned myocardium, while retention of Tl is dependent mainly on RBF.